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Biomedical subjects

T H Shawker

Publications and source records attributed to T H Shawker.

At least 55 records · Page 3Linked to original sources
PubMed1990

von Hippel-Lindau disease: radiologic screening for visceral manifestations.

The visceral manifestations of von Hippel-Lindau (VHL) disease can cause significant morbidity and mortality. The authors prospectively screened 37 persons from a single kindred. Twenty-five subjects underwent abdominal ultrasound (US), contrast material-enhanced abdominal computed tomography (CT), and nonenhanced abdominal magnetic resonance (MR) imaging. Eight subjects younger than 16 years of age underwent abdominal US and MR imaging only. Scrotal US was employed in 25 male patients. Eleven subjects had renal cysts or tumors. Contrast-enhanced CT depicted renal abnormalities in 10 of these subjects, US in seven, and MR imaging in nine. Among 12 subjects with pancreatic cysts or tumors, CT showed pancreatic abnormalities in all 12, US in nine, and MR imaging in nine. Three subjects (mean age, 34.5 years) had renal tumors, and three had pancreatic masses. Scrotal US revealed epididymal cystadenomas in seven subjects; two of these tumors were surgically verified. A combination of contrast-enhanced CT and scrotal US in male patients appears to be the best way to screen for visceral manifestations of VHL disease.

Adolescent↗
PubMed1990

Ultrasound guidance improves the success rate of internal jugular vein cannulation. A prospective, randomized trial.

STUDY OBJECTIVE: To compare conventional versus ultrasound-guided internal jugular vein cannulation techniques. DESIGN: Patients were randomly assigned to receive either conventional or two-dimensional ultrasound-guided internal jugular vein cannulation. Patients who could not be cannulated with five or fewer passes by either technique, were crossed over to the other technique. SETTING: Clinical research unit in a tertiary care center. PATIENTS: All consecutive patients who required urgent or urgent-elective internal jugular vein cannulation during the study period. INTERVENTIONS: The two-dimensional ultrasound transducer imaged all cannulation attempts. For patients randomized to ultrasound guidance, the operator viewed two-dimensional ultrasound images, and received verbal guidance from the ultrasound technician. For patients randomized to the conventional arm, two-dimensional ultrasound images were recorded without visual or verbal feedback. MEASUREMENTS AND MAIN RESULTS: Two-dimensional ultrasound was significantly better than conventional guidance in reducing the number of failed site cannulations from 6/17 (35 percent), to 0/12 (0 percent), p less than 0.05. Two-dimensional ultrasound also reduced the mean number of passes required to cannulate the vein from 3.12 to 1.75 (p less than .05), and was also successful in six/six (100) of patients who failed cannulation by conventional means (p less than 0.05). CONCLUSIONS: Intensivists can increase successful internal jugular vein cannulation using ultrasound guidance. Two-dimensional ultrasound should be considered for patients difficult to cannulate or those at high risk of cannulation complications.

Catheterization, Central Venous↗
PubMed1989

Prevalence of gallstone disease in Hispanic populations in the United States.

The 1982-1984 Hispanic Health and Nutrition Examination Survey used ultrasonography to investigate the epidemiology of gallstone disease. Mexican American, Cuban American, and Puerto Rican men and women, aged 20-74 yr, were selected from household samples in Texas, New Mexico, Arizona, Colorado, California, Connecticut, New Jersey, New York, and Florida. Ultrasonography was performed on 2299 persons. The age-adjusted prevalence of gallstone disease (gallstones + cholecystectomy) among Mexican American men (7.2%) was 1.7 times that of Cuban American men and 1.8 times that of Puerto Rican men. The prevalence for Mexican American women (23.2%) was 1.5 times that of Cuban American women and 1.7 times that of Puerto Rican women. Rates were about three times higher among women than men and increased with age in both sexes and all ethnic groups except older Puerto Rican women. Among Mexican American women aged 60-74 yr, the prevalence of gallstone disease reached 44.1%. These results support the hypothesis that Mexican Americans are at increased risk of gallstone disease.

Aged↗
PubMed1989

Efficacy of a gonadotropin-releasing hormone agonist in the treatment of uterine leiomyomata: long-term follow-up.

The authors employed a gonadotropin-releasing hormone agonist (GnRH-a) (D-His6-pro9-NET-GnRH) to treat 19 patients with symptomatic uterine leiomyomata, by daily subcutaneous injections (4 micrograms/kg) for 6 months. After therapy, patients were followed for 6 months without any therapy. Uterine volumes were measured by serial pelvic examinations and pelvic sonography. Measurements of serum estradiol, luteinizing hormone, and follicle-stimulating hormone were used to assess treatment response. Pituitary desensitization and hypoestrogenemia were achieved in all within 8 weeks, and in 18 of 19, hypoestrogenemia was maintained for the duration. Uterine volume at the conclusion of therapy (207.5 +/- 152.7 ml) was significantly reduced in all patients when compared with pretreatment sizes (420.8 +/- 276.4, P less than 0.05). Side effects included hot flashes (78%), vaginal dryness (32%), and transient frontal headaches (55%). All patients reported partial or complete relief from their symptomatic leiomyomata. Uterine volume at the conclusion of follow-up (345.4 +/- 195.7 ml) was greater than at the conclusion of therapy. Menses resumed in all patients within 4 to 8 weeks. In conclusion, GnRH-a therapy does not provide definitive therapy for symptomatic uterine leiomyomata but is effective in reducing the size of leiomyomata as a temporary measure. Gonadotropin-releasing hormone agonist therapy may be useful as an adjunct before myomectomy or hysterectomy and deserves further investigation.

Adult↗
PubMed1989

Quantitative ultrasonic detection and classification of diffuse liver disease. Comparison with human observer performance.

A multiparameter ultrasonic tissue characterization system has been developed and tested on several types of diffuse liver disease. The four tissue characterization parameters used are based on the first and second order statistics of the B-scan image. Performance of the system was evaluated using receiver operating characteristic (ROC) analysis and was compared with the performance of experienced human observers viewing B-scan images. The machine-based multiparameter system achieved an area under the ROC curve (Az) of 0.88 for detection of chronic hepatitis in more than 100 proven cases of the disease. This was dramatically better than the performance of human observers (Az = .64, P less than .05) and compares favorably to the performance of other accepted diagnostic tests such as head CT and the PAP smear. For detection of Gaucher's disease, the Az for the system was .92, whereas for separating hepatitis from Gaucher's disease Az was .84. Human observers also did well at these tasks (P greater than .8) using organomegaly as their major criterion for diagnosing Gaucher's disease. For primary biliary cirrhosis the system Az was .80, for glycogen storage disease Az was .94. These results suggest that use of multiparameter tissue characterization can significantly increase the usefulness of ultrasound for evaluation of diffuse liver disease.

Gaucher Disease↗
PubMed1989

Prospective evaluation of hepatic imaging studies in the detection of colorectal metastases: correlation with surgical findings.

Nineteen patients with isolated colorectal liver metastases were preoperatively evaluated with five hepatic imaging studies. The results of these studies were correlated with operative findings. One study involved the use of EOE-13, an intravenously administered lipid contrast agent that enhances liver parenchyma on computed tomography (CT) scans (EOE-CT). Another study, arterial portography (AP-CT), was performed with injection of a water-soluble contrast agent into the superior mesenteric artery during CT scanning. Delayed CT scanning (DS-CT) was completed 4 hours after AP-CT. In addition, T1- and T2-weighted magnetic resonance imaging (MRI) (T1-MRI, T2-MRI) scans were done. All patients subsequently underwent laparotomy with identification of 78 lesions. A lesion-by-lesion analysis revealed that the sensitivity of EOE-CT (83%), AP-CT (78%), DS-CT (82%), and T1-MRI (84%) was comparable. T2-MRI had a significantly lower sensitivity (64%) compared with EOE-CT, DS-CT, and T1-MRI. The false-positive rate for AP-CT was 31%, which was significantly higher than that of all other studies. The T1-MRI examination had the lowest false-positive rate and proved to be the best hepatic imaging study in the detection of colorectal metastases. EOE-CT and DS-CT were comparable, whereas AP-CT and T2-MRI proved to be inferior tests.

Colorectal Neoplasms↗
PubMed1989

Localization of islet cell tumors.

In summary, although similar imaging techniques are used for the localization of insulin and gastrin secreting islet cell tumors, the success rates are very different. Fortunately, the best results are obtained in the tumor for which effective medical treatment is less available, namely insulinomas, which can be found and successfully resected in over 90 per cent of patients. Both portal venous sampling and experienced intraoperative ultrasound are critical for successful surgery of small insulin-secreting tumors. Facilities without these resources should not explore patients when the conventional imaging studies are negative. Gastrinomas, on the other hand, will elude detection by even the most experienced surgeons in over 20 per cent of patients with sporadic Zollinger-Ellison syndrome in spite of positive portal venous sampling and intra-arterial secretin studies. The very small size of these tumors and their occurrence in more difficult to explore extrapancreatic sites provides the basis for this difference. However, patients with negative imaging studies and negative surgical explorations have an excellent prognosis on long-term follow-up when gastric acid hypersecretion is controlled. An annual computed tomographic scan is recommended since the appearance of a tumor would mandate surgical resection because of the significant incidence of malignancy in larger tumors. However, progression to imageable tumors has been unusual in our experience with this group of patients. There remains a small group of patients with highly malignant, rapidly metastasizing, gastrin-secreting islet cell carcinomas for whom localization is simple but of little relevance. However, locally invasive gastrinomas may often be resectable and provide prolonged remission and even cure. Aggressive surgery, supported by detailed cross-sectional and angiographic localization, has a role in this small group of patients.

Adenoma, Islet Cell↗
PubMed1989

Ultrasound sector scanning used to define changes in muscle configuration.

Dynamic configurational changes in the rectus femoris muscle were examined using a real time ultrasound sector scanner in ten normal subjects. The angle of passive knee flexion was varied as transverse ultrasound scanning was performed at the mid-transverse thigh. Configurational changes in the rectus femoris were computed from a traced outline of the muscle and the geometric center of the mass was calculated at all degrees of knee flexion. The geometric center of the mass varied with knee position. The anterioposterior dimensions and cross sectional areas of the rectus femoris and vastus intermedius remained constant, however, despite changes in knee position. The pattern of change observed was reproducible and reflects consistent changes in muscle configuration. The technique and instrumentation should have value for non-invasive dynamic and static observation of individual muscles.

Adult↗
PubMed1988

Intraoperative ultrasonographic localization of islet cell tumors. A prospective comparison to palpation.

The purpose of the present study was to evaluate prospectively the value of intraoperative ultrasound scanning (IOUS) in localizing islet cell tumors by comparing results of IOUS to those of palpation during 44 consecutive laparotomies for gastrinoma (36) or insulinoma (8). All patients had preoperative radiographic imaging studies and selective venous sampling for hormones, which guided the subsequent laparotomy. Any suspicious finding by palpation and/or IOUS was resected. Pathologic evidence of islet cell neoplasm served as the reference standard. Five patients were excluded from analysis because neither palpation nor IOUS had suspicious findings and no islet cell tumor was found. Seven pancreatic insulinomas were found in seven patients. IOUS was as sensitive as palpation at localizing insulinomas. Twenty-three pancreatic gastrinomas were found in 19 patients. IOUS was equal to palpation in the ability to localize gastrinomas. Gastrinomas that were successfully imaged by IOUS were significantly larger than gastrinomas that were not imaged. Twelve extrapancreatic gastrinomas were found in nine patients, and palpation was more sensitive than IOUS at localizing these small duodenal wall tumors. Five patients (11%) had their surgical management changed by IOUS. Two patients had pancreatic tumors (one gastrinoma and insulinoma) enucleated that would not have been found without IOUS, and three patients had resections of pathologically proven malignant islet cell tumors based on sonographic findings. All five patients were cured with short follow-up. The present results demonstrate that palpation and IOUS are complementary because IOUS can image tumors that are not palpable and IOUS can provide additional information concerning malignant potential not detected by palpation.

Adenoma, Islet Cell↗
PubMed1988

Cross-sectional tongue shape during the production of vowels.

This study used ultrasound imaging to examine the cross-sectional shape of the tongue during the production of the ten English vowels ( see text ) in two consonant contexts--/p/ and /s/--and at two scan angles--anterior and posterior. Results were compared with models of sagittal tongue shape. A newly built transducer holder and head restraint maintained the ultrasound transducer in a fixed position inferior to the mandible at a chosen location and angle. The transducer was free to move only in a superior/inferior direction, and demonstrated reliable tracking of the jaw. Since the tongue is anisotrophic along its length, anterior and posterior scan angles were examined to identify differences in tongue shape. Similarly, the coarticulatory effects of the sibilant /s/ versus the bilabial /p/ were examined, to assess variability of intrinsic tongue shape for the vowels. Results showed that the subject's midsagittal tongue grooving was almost universal for the vowels. Posterior grooves were deeper than anterior grooves. In /s/ context, posterior tongue grooves were shallower than in /p/ context. Anteriorly, /s/ context caused deeper grooves for low vowels. Cross-sectional tongue shape varied with tongue position similarly to sagittal tongue shape.

Adult↗
PubMed1988

Hepatosplenic candidiasis: wheels within wheels.

Eight immunocompromised cancer patients with tissue-proved candidiasis underwent serial abdominal ultrasound (US) and computed tomography (CT). At US, four patterns of hepatic and splenic candidiasis were recognized, one of which the authors call a "wheels-within-wheels" pattern. In addition, periportal linear areas of increased attenuation, possibly calcified, were identified at follow-up, nonenhanced CT. Some abscesses were better seen on nonenhanced CT scans, while others became visible only with enhancement. Although lesions not seen at US were often seen at CT, the opposite was also true. In two cases, pathologic proof of candidiasis was established even when all imaging studies were normal. For maximum imaging sensitivity, patients should be studied with US and nonenhanced and enhanced CT. Even when both US and CT scans are negative, if there is a strong clinical suggestion of candidiasis, open biopsy is recommended.

Abscess↗
PubMed1988

Fournier gangrene: diagnosis with scrotal US.

Skin thickening and subcutaneous air were detected at ultrasound (US) of the scrotum in a patient with normal-appearing testicles and signs and symptoms suggestive of an acute inflammatory process, such as epidydimitis or orchitis. The patient was found to have Fournier gangrene. In more advanced cases, US can demonstrate that this skin thickening and subcutaneous air extends posteriorly to include the perineum and buttocks. Because of the high mortality of this mixed anaerobic and aerobic infection, it is important to recognize Fournier gangrene early so that the correct surgical and medical treatment can be promptly instituted. To the authors' knowledge, this is the first description of the US characteristics of Fournier gangrene.

Fasciitis↗
PubMed1988

Hepatic candidiasis in cancer patients: the evolving picture of the syndrome.

Focal hepatosplenic candidiasis has been recognized with increasing frequency in recent years. We reviewed the cases of eight patients seen between 1982 and 1985, and information on 60 patients whose cases have been reported in the world literature. The characteristics of focal hepatosplenic candidiasis include persistent fever in a neutropenic patient whose leukocyte count is returning to normal, often coupled with abdominal pain; an elevated alkaline phosphatase level; and less commonly, rebound leukocytosis. The characteristic "bull's eye" lesions seen with hepatic ultrasound examination or computed tomography generally are not detectable until neutrophil recovery has occurred. Diagnosis can be established only by biopsy evidence of yeasts or pseudohyphae in the granulomatous lesions. Cultures are frequently negative, however, especially in patients who have been pretreated with antifungal agents. We review the evolving nature of hepatosplenic candidiasis, focusing on diagnosis and treatment.

Adolescent↗
PubMed1988

The ultrasound appearance of radiation-induced hepatic injury. Correlation with computed tomography and magnetic resonance imaging.

The ultrasound findings in three cases of radiation-induced hepatic injury are described and compared with computed tomography and magnetic resonance imaging findings. Fatty infiltration of the liver was present in two of the cases in which concurrent chemotherapy was being administered. On ultrasound B-scans, the regions of radiation injury were hypoechoic relative to the remainder of the liver. This finding was more obvious in the patients with fatty livers. CT scans on the patients with fatty infiltrated livers showed higher attenuation in the irradiated region than in unexposed liver. In the patient where no fatty infiltration was present, the radiated section of liver had lower attenuation consistent with previous reports. Magnetic resonance imaging showed decreased signal in the exposed areas on T1 weighted images.

Child, Preschool↗
PubMed1987

Comparison of angiography and ultrasound in the evaluation of the portal venous system in pancreatic carcinoma.

Detailed images of upper abdominal vascular anatomy can now be obtained by experienced operators using modern real-time ultrasound scanners. To help determine the role of real-time ultrasound in preoperative evaluation of pancreatic carcinoma, ultrasound and angiographic results were compared in a series of 45 patients admitted with documented carcinoma of the pancreas. When surgical results were available, these were compared with the ultrasound and angiographic findings. The main tributaries of the portal system were evaluated with ultrasound and angiography for evidence of compression, displacement, or occlusion. A sensitivity of 90% and specificity of 95% were achieved for splenic vein abnormalities by ultrasound compared to angiography. For portal vein evaluation, sensitivity was 75%, and specificity was 100%, whereas for the superior mesenteric vein a sensitivity of 100% and a specificity of 94% were attained. Ultrasound can make angiography prior to laparotomy unnecessary in many cases if thorough evaluation of the portal venous system is emphasized during the initial ultrasound study.

Humans↗